$namespace: 'ym' !default;
$block-sel: '-' !default;
$element-sel: '__' !default;
$modify-sel: '--' !default;

@mixin b($block){
  .#{ $namespace + $block-sel + $block}{
    @content;
  }
}

@mixin e($element){
  $parentSeletor: &;
  @at-root {
    #{ $parentSeletor + $element-sel + $element}{
      @content;
    }
  }
}

@mixin m($modify){
  $parentSeletor: &;
  @at-root {
    #{ $parentSeletor +  $modify-sel + $modify}{
      @content;
    }
  }
}